Engine

ABSTRACT

Embodiments are directed toward an engine. In some embodiments, the engine includes a water pump and a balancer shaft. In some embodiments, the water pump has a plain bearing. In some embodiments, plain bearing is supplied with pressurized oil. In some embodiments, the balancer shaft drives the water pump as well as cam shafts.

FIELD OF THE INVENTION

The invention relates generally to engines for vehicles includingoff-road vehicles, such as all-terrain vehicles and side-by-side utilityand sport vehicles.

BACKGROUND OF THE INVENTION

Some measures of performance of off-road vehicles (for example,off-highway vehicles such as all-terrain vehicles (ATVs), side-by-sideutility vehicles (UTVs), snowmobiles, or others) improve as the weightof the vehicle decreases and as engine power increases. Additionally,off-road vehicles can operate in harsh conditions and terrain.Therefore, there remains a need for improved engines having properlubrication and cooling, while providing smooth power delivery, as wellas ample power and torque.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide enginesfor off-road vehicles having the requisite horsepower and torque.

In some versions, the engine has a water pump and a balancer shaft. Insome embodiments, the water pump has a plain bearing that is suppliedwith pressurized oil. In some embodiments, the balancer shaft drives thewater pump.

In some versions, the engine has an engine housing. In some embodiments,the engine housing has an exterior surface and a spacer that defines asupport surface that is spaced apart from the exterior surface of theengine housing. In some embodiments, the water pump is coupled to thesupport surface and spaced apart from the exterior surface of the enginehousing.

In some versions, the water pump has a coolant return port. In someembodiments, the coolant return port is coaxial with the spacer.

In some versions, the balancer shaft is housed in the engine housing. Insome embodiments, the water pump has an impeller. In some embodiments,the balancer shaft drives the impeller of the water pump.

In some versions, the engine includes a water pump drive shaft. In someembodiments, the water pump drive shaft extends through the spacer. Insome embodiments, the water pump drive shaft drives the impeller. Insome versions, the engine includes a balancer driven gear. In someembodiments, the balancer driven gear is housed in the engine housing.In some embodiments, the balancer driven gear drives the water pumpdrive shaft. In some embodiments, the balancer shaft drives the balancerdriven gear.

In some versions, the water pump has a plain bearing that is suppliedwith pressurized oil. In some embodiments, the water pump drive shafthas the plain bearing that is supplied with pressurized oil. In someembodiments, the spacer has a tubular structure. In some embodiments,the tubular structure defines the plain bearing. In some embodiments,the water pump drive shaft has a proximal end portion and an oppositedistal end portion coupled to the impeller. In some embodiments, thewater pump drive shaft extends through the plain bearing. In someembodiments, the engine includes a radial seal ring. In someembodiments, the radial seal ring is disposed opposite the plain bearingfrom the proximal end portion of the water pump drive shaft. In someversions, the engine includes a water pump seal. In some embodiments,the water pump seal is disposed between the impeller and the radial sealring.

In some versions, the spacer includes a male spacer portion and a femalespacer portion that is configured to receive the male spacer portion. Insome versions, one of the male spacer portion or the female spacerportion is integral to the engine housing. In some embodiments, anotherof the male spacer portion or the female spacer portion is separablefrom the engine housing. In some versions, the separable spacer portion(for example, the male spacer portion) defines the support surface. Insome embodiments, the support surface includes a flange. In someembodiments, at least a portion of the support surface (for example, theflange) defines a portion of a water pump housing that houses theimpeller of the water pump.

In some versions, the engine housing includes a crankcase. In someembodiments, the crankcase defines the exterior surface. In someembodiments, the spacer extends from the exterior surface of thecrankcase. In some versions, the engine housing includes a gear housing(for example, a portion of the crankcase may include the gear housing)that houses one or more gears. In some embodiments, the gear housingdefines the exterior surface. In some embodiments, the spacer extendsfrom the exterior surface of the gear housing.

In some versions, the engine housing has a first side portion and asecond side portion that is opposite the first side portion. In someembodiments, the gear housing is disposed on the first side portion ofthe engine housing. In some embodiments, the gear housing defines theexterior surface. In some embodiments, the exterior surface faces thesecond side portion of the engine housing.

In some versions, the engine includes a timing chain. In someembodiments, the balancer shaft drives the timing chain and, in someembodiments, drives both the timing chain and the impeller of the waterpump.

In some versions, the engine includes one or more camshafts, a firstintake valve, and a second intake valve. In some embodiments, the timingchain drives the one or more camshafts. In some embodiments, each of thefirst intake valve and the second intake valve is transitionable betweena respective closed configuration and a respective open configuration.In some embodiments, each of the first intake valve and the secondintake valve has a respective lift amplitude corresponding to therespective open configuration. In some embodiments, the one or morecamshafts define the respective lift amplitudes of the first intakevalve and the second intake valve. In some embodiments, the respectivelift amplitude of the first intake valve is greater than the respectivelift amplitude of the second intake valve.

In some versions, the engine preferably includes a cylinder bore and acrankshaft. The cylinder bore preferably defines a central axis. In someembodiments, the crankshaft defines a rotational axis. In someembodiments, the rotational axis of the crankshaft extends along a planethat is parallel to the central axis of the cylinder bore. In someembodiments, the central axis of the cylinder bore is offset from theplane.

In some versions, the crankcase has a split that extends along a plane.In some embodiments, the balancer shaft defines a rotational axis. Insome embodiments, the rotational axis of the balancer shaft and therotational axis of the crankshaft extend along the plane along which thesplit of the crankcase extends.

In some versions, the crankshaft is monolithic. In some embodiments, theengine is a single-cylinder engine (i.e., the engine has no more thanone cylinder).

In some versions, the crankshaft defines an oil bore. In someembodiments, the oil bore extends along the rotational axis of thecrankshaft. In some versions, the crankshaft has a bearing (for example,a main bearing or a support bearing). In some embodiments, the oil borehas an outlet. In some embodiments, the outlet is spaced apart from thebearing. In some embodiments, the oil bore provides pressurized oil fromthe bearing to the outlet.

In some embodiments, the engine includes a rotor, a nozzle, and an oilflow path. In some embodiments, the nozzle is configured to spraypressurized oil onto the rotor. In some embodiments, the oil flow pathprovides pressurized oil to a bearing of the crankshaft (for example, amain bearing or a support bearing). In some embodiments, the oil flowpath provides pressurized oil from a bearing of the crankshaft (forexample, a main bearing or a support bearing) to the nozzle.

In some versions, the engine includes an oil pan assembly. In someembodiments, the oil pan assembly includes an upper oil pan portion anda lower oil pan portion. In some embodiments, the upper oil pan portionhas an open top portion and an open bottom portion. In some embodiments,the open top portion has a closed bottom. In some embodiments, the openbottom portion has a closed top. In some embodiments, the lower oil panportion is coupled to and separable from the open bottom portion of theupper oil pan portion.

In some versions, the closed bottom of the open top portion of the upperoil pan portion has a drive shaft recess. In some embodiments, the driveshaft recess is configured to at least partially receive a drive shaftof the vehicle. In some versions, the lower oil pan portion is laterallyoffset from the drive shaft recess. In some embodiments, the lower oilpan portion extends below the drive shaft recess.

In some versions, the closed top of the open bottom portion of the upperoil pan portion defines a dipstick access port. In some versions, theopen top portion of the upper oil pan portion defines a first oil drain.In some embodiments, the lower oil pan portion defines a second oildrain. In some versions, the lower oil pan portion has a bottom thatextends along a plane. In some embodiments, at least a portion of theclosed bottom of the open top portion of the upper oil pan portion has aslope relative to the plane. In some embodiments, the slope facilitatesproviding oil from the open top portion of the upper oil pan portion tothe lower oil pan portion. In some embodiments, the slope angles towardthe lower oil pan portion along a path through the upper oil pan portionthat extends from a lateral side of the engine toward the lower oil panportion. In some versions, the slope facilitates providing oil from theopen top portion of the upper oil pan portion over the drive shaftrecess to the lower oil pan portion. In some embodiments, the slopedbottom of the open top pan portion of the upper oil pan portion extendsover the drive shaft recess and angles toward the oil pan portion.

In some versions, the engine has an intake valve and an exhaust valve.In some embodiments, the balancer shaft drives the intake valve and theexhaust valve.

In some versions, the engine has only a single balancer shaft.

In some versions, a cam shaft is driven by the balancer shaft and drivesthe exhaust valve. In some versions, a decompression system is coupledto the cam shaft and is configured to prevent closure of the exhaustvalve until the cam shaft meets or exceeds a predetermined numberrotations per minute. In some versions, a hydraulic valve lash adjusterconfigured to adjust valve lash of the exhaust valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present invention are described in detail below withreference to the following drawings.

FIG. 1 is a front isometric view of an exemplary engine.

FIG. 2 is a rear isometric view of the engine of FIG. 1 .

FIG. 3 is an isometric front view of internal components of the engineof FIG. 1 , showing coolant flow paths of the engine.

FIG. 4 is an isometric rear view of internal components of the engine ofFIG. 1 , showing coolant flow paths of the engine.

FIG. 5 is a right-side elevational view of the engine of FIG. 1 .

FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 5 .

FIG. 7 is a top view of the engine of FIG. 1 .

FIG. 8 is a front isometric view of internal components of the engine ofFIG. 1 .

FIG. 9 is a rear isometric view of internal components of the engine ofFIG. 1 .

FIG. 10 is a right-side elevational view of internal components of theengine of FIG. 1 .

FIG. 11 is a front-side elevational view of internal components of theengine of FIG. 1 .

FIG. 12 is a left-side elevational view of internal components of theengine of FIG. 1 .

FIG. 13 is a rear-side elevational view of internal components of theengine of FIG. 1 .

FIG. 14 is a top view of internal components of the engine of FIG. 1 .

FIG. 15 is a bottom view of internal components of the engine of FIG. 1.

FIG. 16 is a left-side partially exploded isometric view of internalcomponents of the engine of FIG. 1 .

FIG. 17 is a rear-side elevational view of the engine of FIG. 1 .

FIG. 18 is a cross-sectional view taken along line 18-18 in FIG. 17 .

FIG. 19 is a close-up view of a portion of the cross-sectional view ofFIG. 18 .

FIG. 20 is a front view of the engine of FIG. 1 .

FIG. 21 is a cross-sectional view taken along line 21-21 in FIG. 20 .

FIGS. 22-24 are front isometric views of an upper engine portion of theengine of FIG. 1 .

FIG. 25 is a timing chart regarding valves of the engine of FIG. 1 .

FIG. 26 is an alternative timing chart regarding valves of the engine ofFIG. 1 .

FIG. 27 is a cross-sectional view taken along line 27-27 in FIG. 17 .

FIG. 28 is a left-side elevational view of the engine of FIG. 1 .

FIG. 29 is an isometric front view of a crankcase of the engine of FIG.1 .

FIG. 30 is a right-side elevational view of the crankcase of the engineof FIG. 1 .

FIG. 31 is a left-side elevational, partially exploded view of theengine of FIG. 1 .

FIG. 32 is a front-side elevational, partially exploded view of theengine of FIG. 1 .

FIG. 33 is an isometric front view of a crankshaft and balancer shaft ofthe engine of FIG. 1 .

FIG. 34 is a top view of the engine of FIG. 1 .

FIG. 35 is a stepped cross-sectional view taken along stepped line 35-35in FIG. 34 .

FIG. 36 is a close-up view of a portion of the stepped cross-sectionalview of FIG. 35 .

FIG. 37 is an isometric front view of internal components of the engineof FIG. 1 , showing oil flow paths of the engine.

FIG. 38 is an isometric rear view of internal components of the engineof FIG. 1 , showing oil flow paths of the engine.

FIG. 39 is an isometric front, partially exploded view of the engine ofFIG. 1 .

FIG. 40 is a front, partially exploded elevational view of the engine ofFIG. 1 .

FIG. 41 is a front-side elevational view of the engine of FIG. 1 , witha driveshaft of a vehicle in which the engine is installed.

FIG. 42 is a bottom view of the engine of FIG. 1 .

FIG. 43 is a top view of the engine of FIG. 1 .

FIG. 44 is a cross-sectional view taken along line 44-44 in FIG. 43 .

FIG. 45 is a cross-sectional view taken along line 45-45 in FIG. 43 .

FIG. 46 is a cross-sectional view taken along line 46-46 in FIG. 15 ,with the engine being devoid of oil.

FIGS. 47-49 are cross-sectional views taken along line 46-46 in FIG. 15, with the engine containing oil.

FIG. 50 is a front-side elevational view of the engine of FIG. 1 .

FIGS. 51-53 are cross-sectional views taken along line 51-51 in FIG. 50.

FIG. 54 is an isometric view of the crankshaft and balancer shaft of theengine of FIG. 1 , with the crankshaft having dual crankshaft gears thatare spring loaded.

FIG. 55 is an isometric exploded view of the dual crankshaft gears ofFIG. 54 .

FIG. 56 is an isometric, partially exploded view of an end portion of anexhaust cam shaft of the engine of FIG. 1 with a decompression system.

FIG. 57 is an isometric exploded view of a portion of the decompressionsystem of FIG. 56 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1 and 2 , an engine 2 has an engine housing 4 thathouses moving components that facilitate translation of combustionenergy to rotational energy. In some embodiments, components visiblefrom the exterior of the engine 2 include an intake port 6 (for example,an air intake connector or throttle body connector), a blowby port 8, anoil filter 10, an exhaust port 12 (for example, an exhaust manifoldconnector) (see FIG. 2 ), a sparkplug access hole 14, and a crank sensorport 16 (see FIGS. 1, 2 and 7 ). In some embodiments, the housing 4 hasan upper engine portion 30 and a lower engine portion 32 disposed belowand, in some versions, coupled (for example, bolted) to the upper engineportion 30. In some embodiments, an oil pan assembly 34 is disposedbelow and, in some versions, coupled to the lower engine portion 32. Insome embodiments, the engine 2 has a water pump 40 that is external toand, in some versions, coupled to the engine housing 4.

FIGS. 3 and 4 show arrows that provide logical representations ofcoolant flow paths through the engine 2 according to some embodiments.In some embodiments, the water pump 40 draws the coolant from a radiator(not shown) through a first coolant return port 42 and pushes thecoolant through the coolant paths in the upper engine portion 30 througha first coolant out port 44. In some embodiments, the coolant isreturned directly to the water pump 40 through a bypass coolant returnhose 46 that returns the coolant through a second coolant return port 48without going through the radiator until a thermostat 49 opens. In someembodiments, the thermostat 49 opens responsive to the coolant reachingor exceeding a predetermined threshold temperature. In some embodiments,when the thermostat 49 opens, the coolant is redirected to return to theradiator through a second coolant out port 50 (see FIGS. 1, 3, and 4 ).In some embodiments, the central axis of the first coolant out port 44is transverse (for example, perpendicular) to the central axis of thefirst coolant return port 42. In some embodiments, the central axis ofthe second coolant return port 48 is transverse to both the central axisof the first coolant return port 42 and the central axis of the firstcoolant out port 44.

In some embodiments, the water pump 40 is coupled to a surface of theengine housing 4 that faces a lateral side of the engine 2, such as aleft or right facing surface. In some embodiments, the water pump 40 isdisposed on a front portion of the engine housing 4. In someembodiments, the water pump 40 is coupled to the lower engine portion32. In some embodiments, the housing 4 has a crankcase 52, and, in someembodiments, the crankcase 52 is included in the lower engine portion32. In some embodiments, the water pump 40 is coupled to the crankcase52. In some embodiments, the crankcase 52 has a gear housing portion 54that houses one or more gears (see FIG. 6 , which is a cross-sectionalview of taken along line 6-6 in FIG. 5 ; see also FIGS. 31 and 32 ),and, in some embodiments, the water pump 40 is coupled to the gearhousing portion 54. In some embodiments, the gear housing portion 54 isdisposed on a side portion of the engine 2, such as a lateral sideportion of the engine 2. In some embodiments, the water pump 40 iscoupled to a surface of the gear housing portion 54 that faces the sideportion of the engine 2 that is opposite the side portion of the engine2 on which the gear housing portion 54 is disposed. For example, asshown in FIG. 1 , the gear housing portion 54 is disposed on the leftside portion of the engine 2, and the water pump 40 is disposed on aright-facing surface 56 of the gear housing portion 54.

In some embodiments, the water pump 40 is coupled to a support surface,such as water-pump support flange 58. In some embodiments, the enginehousing 4 has a spacer 60 that spaces the support surface away from theexterior surface of the lower engine portion 32 (see FIGS. 6 and 7 ). Insome embodiments, the spacer 60 is parallel to and, most preferably,coaxial with the first coolant return port 42 (see FIG. 6 ). In someembodiments, the spacer 60 includes a male spacer portion 62 and afemale spacer portion 64 that is configured to receive the male spacerportion 62. In some embodiments, one of the male spacer portion 62 orthe female spacer portion 64 is integral to the crankcase 52, and, insome versions, the other is separable from the crankcase 52. In someembodiments, the spacer 60 defined by the male spacer portion 62 and thefemale spacer portion 64 is tubular. In some embodiments, the malespacer portion 62 comprises a portion of the water pump assembly. Insome embodiments, the male spacer portion 62 is inserted into the femalespacer portion 64 upon assembly.

In some embodiments, a water pump drive shaft 66 extends through thespacer 60. In some embodiments, the water pump drive shaft 66 isparallel to and, in some versions, coaxial with the first coolant returnport 42 (see FIG. 6 ). In some embodiments, an outward housing portion68 and the flange 58 or the male spacer portion 62 defines a water pumphousing 70 that houses an impeller 72. In some embodiments, the waterpump drive shaft 66 drives the impeller 72. In some embodiments, thewater pump drive shaft 66 has a plain bearing 74 that, in some versions,is supplied with pressurized oil (see FIG. 6 ). As shown in FIG. 6 , theplain bearing 74 is defined by a tubular structure that is part of themale spacer portion 62 and spaced apart from the outer walls of the malespacer portion 62. In some embodiments, the plain bearing 74 supportsthe water pump drive shaft 66 and is integrally formed as part of themale spacer portion 62. In some embodiments, a radial seal ring 76pressed into place by a compression spring such as a coil spring 77 isdisposed between the plain bearing 74 and the impeller 72 along thelength of the water pump drive shaft 66 and prevents the oil fromentering the coolant side of the water pump 40. In some embodiments, awater pump seal 80 is disposed between the impeller 72 and the radialseal ring 76 to prevent coolant from escaping the water pump 40 towardthe balancer driven gear 78. In some embodiments, the water pump driveshaft 66 couples to the balancer driven gear 78 that is driven by abalancer gear 82 (see FIGS. 6 and 8-16 ). In some embodiments, thebalancer driven gear 78 has a reduced thickness (dimension perpendicularto the radius) relative to the thickness of the balancer gear 82, suchas 80, 70, 60, 50, 40, 30, 20, or less percent of the thickness of thebalancer gear 82. In some embodiments, the balancer driven gear 78 has a1:1 ratio with the balancer gear 82, both in terms of diameter andnumber of teeth. In some versions, the balancer driven gear 78 has onemore or less tooth than the balancer gear 82 (for example, a 51:50ratio). In some embodiments, the balancer gear 82 and the balancerdriven gear 78 can have an appropriate gear ratio, for example wherebythe balancer gear 82 is larger or smaller than the balancer drive gear78. As shown, the water pump 40 is driven by a balancer shaft 84 thatdrives the balancer gear 82.

In some embodiments, the balancer shaft 84 has a timing sprocket 100that drives a timing chain 102 (see FIGS. 6 and 9 ). The arrangement ofthe balancer shaft 84 driving the timing chain 102 (as opposed to acrankshaft driving the timing chain as is typical) facilitatesmaintenance, installation, assembly, or disassembly of the timing chain102 when the crankcase 52 is fully assembled without removing the heador upper engine portion 30 or splitting the crank case 52 to access thetiming chain 102. In some embodiments, a hydraulic tensioner 104tensions the timing chain 102. In some embodiments, the timing chain 102drives one or more cam sprockets, such as an intake cam sprocket 106 andan exhaust cam sprocket 108 (see FIGS. 8-10, 12, and 16 ). In someembodiments, the intake cam sprocket 106 drives an intake camshaft 110,and the exhaust cam sprocket 108 preferably drives an exhaust camshaft112.

In some embodiments, each camshaft has one or more cam lobes thatcontrol one or more corresponding valves. For example, the intakecamshaft 110 may have two intake cam lobes, such as first and secondintake cam lobes 114, 116 that respectively move first and second intakerocker arms (for example, rocker arm 134 in FIG. 18 , which is across-sectional view taken along line 18-18 in FIG. 17 , and FIG. 19 ,which is a close-up view of a portion of FIG. 18 ) that transfer aportion of the rotational energy of the intake camshaft 110 intomovement of first and second intake valves 118, 120. As another example,the exhaust camshaft 112 may have two exhaust cam lobes, such as firstand second exhaust cam lobes 122, 124 that respectively move first andsecond exhaust rocker arms (for example, rocker arm 136 in FIGS. 18 and19 ) that transfer a portion of the rotational energy of the exhaustcamshaft 112 into movement of first and second exhaust valves 126, 128.In some embodiments, a respective hydraulic valve lash adjuster (forexample, valve lash adjuster 130 or valve lash adjuster 132) couples toeach rocker arm to facilitate hydraulically controlling the valve lashof each valve, without manual adjustment (see FIGS. 18 and 19 ). In someembodiments, the hydraulic valve lash adjusters control the valve lashesfor the corresponding valves by limiting an amount of travel of theoutside ends of the rocker arms that contact the valve lash adjusters,which in turn limits the amount of travel of the inside ends of therocker arms that contact the valve stems as the rocker arms rotate onthe inner or outer races of corresponding bearings (for example,bearings 138 and 139 in FIGS. 18 and 19 ) as the cam lobes transferenergy to the rocker arms.

In some embodiments, a decompression system 133 is configured to reducethe compression impedance in the cylinder bore 142 until a predeterminednumber of rotations per minute (RPMs) is met or exceeded by maintainingone or more exhaust valves, such as exhaust valve 126, in an openconfiguration until such RPM threshold is met or exceeded (see FIG. 3 ).In some embodiments, the decompression system includes aneffective-radius adjustment system 133 a (see FIGS. 56 and 57 ). In someembodiments, the exhaust camshaft 112 is configured to receive thesystem 133 a. In some embodiments, the camshaft 112 has a guide pin 133b, and the system 133 a includes a body 133 c that defines a recess 133d that is configured to receive the pin 133 b and prevent the body 133 cfrom rotating relative to the camshaft 112. In some embodiments, thecamshaft 112 defines a circumferential recess 133 e that is configuredto receive a ring 133 f that is configured to sandwich the system 133 aagainst the exhaust cam lobe 122. In some embodiments, the system 133 ahas a moveable component that adjusts the effective radius of theexhaust cam lobe 122 when the component moves. In some embodiments, thecomponent includes an asymmetrical pin 133 g that defines a largeportion 133 h and a small portion 133 i that are circumferentiallyoffset from each other, such as offset from each other by approximately90°. In some embodiments, the exhaust cam lobe 122 defines a recess 133j that is configured to receive the asymmetrical pin 133 g such that,when the small portion 133 i faces away from the bottom surface of therecess 133 j (not shown), the effective radius of the cam lobe 122 isless than when the large portion 133 h faces away from the bottomsurface of the recess 133 j as found in the orientation shown in FIGS.56 and 57 . In some embodiments, the large portion 133 h is configuredto extend beyond the outer working surface of the cam lobe 122 when thelarge portion 133 h faces away from the bottom surface of the recess 133j. In some embodiments, when the small portion 133 i faces away from thebottom surface of the recess 133 j, the small portion 133 i and thelarge portion 133 h are configured to be flush with or below the outerworking surface of the cam lobe 122.

In some embodiments, the system 133 a includes a lever 133 k that pivotsabout a pin 1331 when the centrifugal force on the lever 133 k issufficient to overcome a bias force applied to the lever 133 k by aspring mechanism 133 m. In some embodiments, the lever 133 k defines arecess 133 n that is configured to receive an arm 133 o that radiallyextends from the pin 133 g so as to rotate the pin 133 g when the lever133 k pivots. Accordingly, in some embodiments, the spring mechanism 133m is configured to apply a bias force that defines the threshold RPMs atwhich the effective radius of the cam lobe 122 is changed. In someembodiments, the effective radius of the cam lobe 122 is configured toreduce when the threshold RPMs are met or exceeded. In some embodiments,reducing the effective radius of the cam lobe 122 decreases the distancethat the rocker arm of the exhaust valve 126 is moved by the cam lobe122, thereby allowing the exhaust valve 126 to enter the closedconfiguration. In some embodiments, increasing the effective radius ofthe cam lobe increases the distance that the rocker arm of the exhaustvalve 126 is moved by the cam lobe 122, thereby preventing the exhaustvalve 126 from entering the closed configuration and maintaining theexhaust valve 126 in the open configuration to reduce the compressionimpedance in the cylinder bore 142.

In some embodiments, the rocker arm for the exhaust valve 126 rides on aball surface (see FIG. 19 ), thereby enabling the rocker arm to pivotinto and out of the page in FIG. 19 . In some embodiments, the system133 a is configured to prevent such pivoting of the rocker arm for theexhaust valve 126. For example, in some embodiments, the pin 133 g isconfigures to extend at least halfway across the exhaust cam lobe 122(for example, 50, 70, 80, 90, or 100 percent across the exhaust cam lobe122. As shown in FIG. 56 , the pin 133 g is configured to extendapproximately one third of the way across the cam lobe 122.

FIG. 21 (which is a cross-sectional view taken along line 21-21 in FIG.20 ) and FIGS. 22-24 show the intake valves 118, 120 and exhaust valves126, 128 in various states, including (a) all valves 118, 120, 126, 128in a closed configurations (see FIGS. 21 and 22 ), (b) the intake valves118, 120 in an open configuration and the exhaust valves 126, 128 in aclosed configuration (see FIG. 23 ), and (c) the intake valves 118, 120in the closed configuration and the exhaust valves 126, 128 in an openconfiguration (see FIG. 24 ). In some versions, the intake valves 118,120 have the same lift and timing curves as each other, and the exhaustvalves 126, 128 have the same lift and timing curves as each other (seeFIG. 25 ). In other versions, the intake valves 118, 120 may havedifferent lift and timing curves than each other to facilitateincreasing swirl and mixing of the fuel and air within the cylinder andpromote complete combustion (see FIG. 26 ).

In some embodiments, the valve stems of the intake valves 118, 120 areoriented transverse to the valve stems of the exhaust valves 126, 128,and all of the valve stems are in some versions oriented transverse tothe center axis 140 of the cylinder bore 142 (see FIGS. 18 and 27 ,which are cross-sectional views taken along lines 18-18 and 27-27 inFIG. 17 ). FIGS. 18 and 27 show the positions and orientations of theinternal components of the upper engine portion 30 relative to theinternal components of the lower engine portion 32. In some embodiments,the center axis 140 of the cylinder bore 142 is offset from therotational axis 144 of the crankshaft 146 (see FIG. 18 ), which extendsalong plane 148 that is parallel to the center axis 140 of the cylinderbore 142 (see FIGS. 18 and 27 ), to reduce friction during an expansionphase of the combustion cycle. In some embodiments, the offset is 2, 3,4, 5, 6, 7 or more millimeters. In some versions, the center axis 140 isdisposed forward of the rotational axis 144. In some versions where thecenter axis 140 is disposed transverse to the vertical direction 150when the engine 2 is in the default orientation (see FIG. 28 ), thecenter axis 140 is disposed above the plane 148 and, in some versions,forward of the plane 148 (see FIGS. 18 and 27 ).

In some embodiments, the center axis 140 of the cylinder bore 142 istransverse (for example, perpendicular) to a plane 170 in which thesplit 172 in the crankcase 52 lies (see FIGS. 18, 27, and 28 ). In someembodiments, the split 172 is transverse to the plane 152 in which themajor bottom surface of the oil pan assembly 34 lies and, in someversions, to the plane 154 in which the split in the oil pan assembly 34lies. In some versions, one or more of the center axis 140 or the split172 may be oriented at an angle (for example, angle 174, angle 176,angle 178, or angle 180) of 5, 10, 15, 20, 25, 30, or more degreesrelative to the vertical direction 150 or the horizontal direction whenthe engine 2 is in the default orientation. In some embodiments, thesplit 172 is horizontal when the bottom of the crankcase 52 rests on ahorizontal surface (see FIG. 29 ).

In some embodiments, one or more of the crankshaft 146 or the balancershaft 84 at least partially extend along the plane 170 in which thesplit 172 in the crankcase 52 lies (see FIGS. 18, 28, and 29 ). In someembodiments, one or more of the rotational axis 144 of the crankshaft146 or the rotational axis 182 of the balancer shaft 84 extend along theplane 170 in which the split 172 in the crankcase 52 lies (see FIGS. 18and 28 ). In some embodiments, the rotational axes 144 and 182 areoriented parallel to the plane 170 (see FIG. 28 ). In some embodiments,the rotational axis 182 of the balancer shaft 84 is disposed forward ofthe rotational axis 144 of the crankshaft 146. In some versions wherethe center axis 140 is disposed transverse to the vertical direction 150when the engine 2 is oriented in the default orientation, the rotationalaxis 182 of the balancer shaft 84 is disposed above the rotational axis144 of the crankshaft 146.

In some embodiments, the crankshaft 146 is monolithic, as opposed to athree-piece crankshaft as typically found in single-cylinder engines(see FIGS. 18, 27, 33, 35, and 36 ). In some embodiments, the crankshaft146 has a crank gear 190 that engages and drives the balancer gear 82(FIG. 33 ). In some embodiments, the crank gear 190 has a 1:1 ratio withthe balancer gear 82, both in terms of diameter and number of teeth. Insome versions, the crank gear 190 has one more or less tooth than thebalancer gear 82 (for example, a 51:50 ratio) to facilitate improvingwear behavior compared to a 1:1 ratio for number of teeth in which thesame tooth of one gear always hits the same countertooth in the othergear. In some versions, one or both of the crank gear 190 and thebalancer gear 82 may include two gears, such as gears 190 a, 190 b (seeFIGS. 54 and 55 ) that are spring loaded relative to each other tofacilitate absorbing gear backlash (i.e., gearlash) and reducing gearnoise. For example, the crank gear 190 may be formed of two adjacent,concentric gears 190 a, 190 b, wherein a first one of the gears 190 a isfixed relative to the crankshaft 146 while the second gear 190 b isrotatable relative to the crankshaft 146 and the first gear 190 a, withone or more springs such as springs 191 a-c pre-loading the two gears190 a, 190 b relative to each other. Such an arrangement preferablyfacilitates a tooth face of the first gear 190 a and an oppositelyfacing tooth face of the second gear 190 b defining a tooth receptaclethat receives a corresponding tooth of the balancer gear 82 betweenthose tooth faces such that those tooth faces press the opposite facesof the received tooth of the balancer gear 82 to facilitating absorbingbacklash. As shown in FIG. 55 , the first gear 190 a preferably definesone or more recesses, such as recesses 191 d-f, that are configured toreceive the springs 191 a-c. The second gear 190 b preferably definesone or more holes, such as holes 191 g-i, that are configured to receivethe springs 191 a-191 c. One or more rings, such as rings 191 j, 191 k,are configured to secure the position of the second gear 190 b along thelongitudinal axis of the crankshaft 146 while allowing the second gear190 b to rotate relative to the first gear 190 a.

In some embodiments, the crank gear 190 has a thickness that is equal tothe thickness of the balancer gear 82. In some embodiments, thecrankshaft 146 has a drilled oil bore that extends to one or more mainbearings or support bearings, such as a main bearing 192, a main bearing194, or a main bearing 196, which in some versions are each plainbearings (see FIG. 36 , which is a close-up view of a portion of FIG. 35, which is a cross-sectional view taken along line 35-35 in FIG. 34 ).For example, an oil bore such as one or more of oil bores 197 a-d (seeFIGS. 9, 11, 14-16, and 33 ; not shown in FIG. 36 because they are in adifferent plane due to the rotational position of the crankshaft 146 asshown in FIG. 36 ) represented by arrow 198 in FIG. 36 may extend fromthe main bearing 192 to an oil bore 200 that in some versions extendsalong the rotational axis 144 of the crankshaft 146 and, in someversions, transfers the oil to one or more nozzles, such as a nozzle 202or an oil-mist-supply opening 204 (see FIG. 36 ). In some embodiments,the nozzle 202 supplies oil to the needle bearing 202 a that surroundsit. In some embodiments, the oil-mist-supply opening 204 is configuredto receive oil mist as indicated by the corresponding arrow in FIG. 36(for example, in embodiments devoid of pressure oil supply). In otherembodiments, the opening 204 is nonexistent or is plugged (for example,in embodiments employing pressurized oil supply). In some embodiments,oil that is provided to the main bearing 192 of the crankshaft 146 issubsequently transferred to a nozzle 206 that sprays the oil onto therotor 208 (see FIGS. 36-38 ).

FIGS. 36-38 show arrows that provide logical representations of oil flowpaths through the engine 2 according to some embodiments. In someembodiments, an oil pump 220 draws the oil from the oil pan assembly 34and pressurizes the oil along the oil flow paths throughout the engine 2(see FIGS. 37 and 38 ). In some embodiments, the oil pump 220 pulls theoil through a pickup strainer 222 disposed in a lower oil pan portion224 of the oil pan assembly 34. In some embodiments, the engine 2 hasone or more of a first oil-line connection port 226 or a second oil-lineconnection port 228 that facilitate providing oil to or from an externaloil cooler (not shown) (see FIG. 1 ).

In some embodiments, the top of the lower oil pan portion 224 couples tothe bottom of an upper oil pan portion 230 (see FIG. 39 ). In someembodiments, the upper oil pan portion 230 has an open top portion 232and an open bottom portion 234 (see FIG. 40 ). In some embodiments, thebottom 236 of the open top portion 232 is closed (for example, halfclosed, majority closed, or entirely closed) (see FIG. 40 ). In someembodiments, the top 238 of the open bottom portion 234 is closed (forexample, half closed, majority closed, or entirely closed). In someembodiments, the open bottom 240 of the upper oil pan portion 230overlaps the open top 242 of the upper oil pan portion 230. For example,as shown in FIG. 41 , the open bottom 240 of the upper oil pan portion230 and the open top 242 of the upper oil pan portion 230 may laterallyextend (from left to right or right to left when viewing the engine 2from the front or the rear, as in FIGS. 41 and 17 ) such that a verticalline (for example, a vertical line 244) may be drawn that extendsthrough both the open bottom 240 and the open top 242 (see FIG. 40 ). Insome embodiments, less than half, and in some versions less than onethird, of the open bottom 240 overlaps the open top 242. In someembodiments, less than half, and most preferably less than one fifth, ofthe open top 242 overlaps the open bottom 240.

In some embodiments, the top 246 of the lower oil pan portion 224 isopen and, in some versions, is configured to correspond to the openbottom portion 234 of the upper oil pan portion 230 (see FIG. 39 ). Insome embodiments, the open top 246 of the lower oil pan portion 224 hasa rim 248 along the perimeter of the open top 246, and the open bottom240 of the upper oil pan portion 230 preferably has a corresponding rim250 along the perimeter of the open bottom 240 that mates with the rim248 of the lower oil pan portion 224 to couple the lower oil pan portion224 to the upper oil pan portion 230. In some embodiments, the open top242 of the upper oil pan portion 230 has a rim 252 around its perimeterthat is configured to correspond to a rim 254 around the perimeter ofthe open bottom 256 of the crankcase 52 to couple the oil pan assembly34 to the crankcase 52 (see FIGS. 39 and 40 ).

In some embodiments, the closed bottom 236 of the open top portion 232of the upper oil pan portion 230 has a drive shaft recess 258 that isconfigured to at least partially receive a drive shaft 260 of thevehicle (see FIG. 41 ). For example, the drive shaft recess 258preferably has a diameter or height that is 5, 10, 15, 20, 25, or morepercent of the diameter of the drive shaft. In some embodiments, thedrive shaft recess 258 laterally aligns with the center axis of thecylinder bore 142 (see FIG. 32 ). In some versions, the drive shaftrecess 258 extends from the front of the upper oil pan portion 230 tothe rear of the upper oil pan portion 230. In other versions, the driveshaft recess 258 extends from the front of the upper oil pan portion 230only partially toward the rear of the upper oil pan portion 230 and, insome versions, less than one half, one third, one quarter, or one fifthof the distance from the front to the rear of the upper oil pan portion230 (see FIG. 42 ). In some embodiments, the lower oil pan portion 224is laterally offset from the drive shaft recess 258 by a distancesufficient to facilitate the lower oil pan portion 224 extending belowthe drive shaft 260. In some embodiments, the closed top 238 of the openbottom portion 234 resides in a plane that is parallel to the plane 154in which the split in the oil pan assembly 34 lies (see FIG. 40 ) and,in some versions, has a dipstick access port 262 through which adipstick 264 extends (see FIG. 46 , which is a cross-sectional viewtaken along line 46-46 in FIG. 5 ). In some embodiments, a first oildrain 266 having an oil drain plug is disposed in the rear face of thelower oil pan portion 224 (see FIG. 2 ), and, in some versions, a secondoil drain 268 having a second oil drain plug is disposed in the closedbottom 236 of the open top portion 232 of the upper oil pan portion 230(see FIGS. 40-42 ).

In some embodiments, the closed bottom 236 of the open top portion 232of the upper oil pan portion 230 has a slope (for example, 25, 30, 35,40, or more degrees) that facilitates guiding oil returned to the oilpan assembly 34 through the open bottom 256 of the crankcase 52 over thedrive shaft recess 258 and into the lower oil pan portion 224 (see FIGS.1, 20, 35, 41 , 42, and 45-50). In some embodiments, the closed bottom236 slopes downward from front to back and, in some versions, slopesdownward from the lateral side opposite the lower oil pan portion 224(for example, the left side of the engine 2) to the lower oil panportion 224. Accordingly, in some embodiments, when the engine 2 isoriented at an angle relative to the default orientation of the engine 2(see FIGS. 48 and 49 ), the oil pan assembly 34 facilitates providingthe oil to the lower oil pan portion 224 and covering the bottom of theoil pickup strainer 222 with oil (see FIG. 46 ).

The crank case 52 preferably defines one or more airflow holes (forexample, cross-drilled holes), such as holes 280-306 (see FIGS. 18, 29,30, and 44 ) that facilitate increasing air flow in and between thevarious internal volumes, such as the volume in the crank case 52 belowthe cylinder bore 142, the volume in gear housing portion 54 or chainhousing, the volume in the upper engine portion 30 or cylinder head, orthe volume in the rotor 208 (for example, the space surrounding thestator). Such an airflow hole arrangement facilitates reducing pumpinglosses thereby improving efficiency and also facilitates reducingtemperatures, such as oil temperature. Moreover, the oil panconfiguration disclosed herein may restrict airflow to the lower end ofthe crank case 52 or the oil pan assembly 34, thereby increasing thebenefits of such an airflow hole arrangement.

As used herein, the following terms take the meanings explicitlyassociated herein, unless the context clearly dictates otherwise. Theterm “or” is an inclusive grammatical conjunction to indicate that oneor more of the connected terms may be employed. For example, the phrase“one or more A, B, or C” or the phrase “one or more As, Bs, or Cs” isemployed to discretely disclose each of the following: i) one or moreAs, ii) one or more Bs, iii) one or more Cs, iv) one or more As and oneor more Bs, v) one or more As and one or more Cs, vi) one or more Bs andone or more Cs, and vii) one or more As, one or more Bs, and one or moreCs. The term “based on” as used herein is not exclusive and allows forbeing based on additional factors not described. The articles “a,” “an,”and “the” include plural references. Plural references are intended toalso disclose the singular.

The terms “front,” “forward,” “rear,” and “rearward” are definedrelative to the engine 2 to orient the reader and do not limit theorientation of the engine 2 in a given application, such as a vehicle.The front side of the engine 2 is shown in FIG. 41 . The terms “front”and “forward” indicate the right side of FIG. 5 or the rightwarddirection when viewing FIG. 5 . The right side of the engine 2 is shownin FIG. 5 . The terms “rear” and “rearward” indicate the left side ofFIG. 28 or in the leftward direction when viewing FIG. 28 . The leftside of the engine 2 is shown in FIG. 28 . The rear side of the engine 2is shown in FIG. 17 . The terms “height,” “vertical,” “upper,” “lower,”“above,” “below,” “top,” “bottom,” “topmost,” and “bottom-most” aredefined relative to the engine 2 to orient the reader and do not limitthe orientation of the engine 2 in a given application, such as avehicle. The top of the engine 2 is shown in FIG. 7 . The bottom of theengine 2 is shown in FIG. 42 . The term “lateral” is defined relative tothe engine 2 to orient the reader and does not limit the orientation ofthe engine 2 in a given application, such as a vehicle. The lateral axisis defined as extending to the left and right sides of the engine 2. Theterm “transverse” refers to a non-parallel orientation and includes yetis not limited to a perpendicular orientation.

The term “in the default orientation” in the context of the engine 2refers to an angle away from the orientation of the engine 2 when aplane 152 in which the major bottom surface of the oil pan assembly 34lies is horizontal (see FIGS. 28 and 47 ) or when a plane 154 in which asplit in the oil pan assembly 34 lies is horizontal (see FIGS. 28 and 47). The term “at an angle relative to the default orientation” in thecontext of the engine 2 refers to an angle away from the orientation ofthe engine 2 when a plane 152 in which the major bottom surface of theoil pan assembly 34 lies is horizontal (see FIGS. 28 and 47 ) or when aplane 154 in which a split in the oil pan assembly 34 lies is horizontal(see FIGS. 28 and 47 ). The orientation of the engine 2 when installedfor a given application, such as a vehicle resting on horizontal ground,may be different than the default orientation. In some embodiments, theangle relative to the default orientation may be up to 15, 20, 25, 30,35, 40, or more degrees.

The term “plain bearing” is used as consistently used in the art ofbearings and refers to a sliding bearing (also known as a slide bearing,solid bearing, journal bearing, or friction bearing). The term“configured” refers to an element being one or more of sized,dimensioned, positioned, or oriented to achieve or provide the recitedfunction or result.

While the preferred embodiments have been illustrated and described, asnoted above, many changes can be made without departing from the spiritand scope of the invention. For example, each disclosure of a componentpreferably having a feature or characteristic is intended to alsodisclose the component as being devoid of that feature orcharacteristic, unless the principles of the invention clearly dictateotherwise. Accordingly, the scope of the invention is not limited by thedisclosure of the preferred embodiment. Instead, the invention should bedetermined entirely by reference to the claims that follow. It shouldalso be noted that the claim dependencies or combinations of elementsrecited in the claims does not reflect an intention to forgo claimingother subject matter disclosed herein. Instead, this disclosure isintended to also disclose the subject matter of any combination of anytwo or more of the claims, such that subsequent claim sets may recitethat any one of the dependent claims depends from any other one or moreclaims, up to and including all other claims in the alternative (forexample, “The engine of any one of the preceding or subsequent claims .. . ”). This disclosure is also intended to disclose the subject matterof any one of the dependent claims, as if it was an independent claim,with or without all or a portion of the subject matter of the originalindependent claim(s) or any other subject matter disclosed herein.

We claim:
 1. An engine comprising: a water pump having a plain bearingthat is supplied with pressurized oil; a balancer shaft that drives thewater pump; an engine housing having an exterior surface; and a spacerthat defines a support surface that is spaced apart from the exteriorsurface of the engine housing, the water pump being coupled to thesupport surface and spaced apart from the exterior surface of the enginehousing.
 2. The engine of claim 1, wherein the water pump has a coolantreturn port that is coaxial with the spacer.
 3. The engine of claim 1,further comprising: a water pump drive shaft that extends through thespacer, the water pump having an impeller, the water pump drive shaftdriving the impeller; and a balancer driven gear housed in the enginehousing, the balancer driven gear driving the water pump drive shaft,the balancer shaft being housed in the engine housing, the balancershaft driving the balancer driven gear.
 4. The engine of claim 1,further comprising a water pump drive shaft that extends through thespacer, the water pump having an impeller, the water pump drive shaftdriving the impeller.
 5. The engine of claim 1, further comprising: awater pump drive shaft that extends through the spacer, the water pumphaving an impeller, the spacer having a tubular structure that defines aplain bearing, the water pump drive shaft having a proximal end portionand an opposite distal end portion coupled to the impeller, the waterpump drive shaft extending through the plain bearing and driving theimpeller; and a radial seal ring disposed opposite the plain bearingfrom the proximal end portion of the water pump drive shaft.
 6. Theengine of claim 5, further comprising a water pump seal disposed betweenthe impeller and the radial seal ring.
 7. The engine of claim 1, whereinthe spacer includes a male spacer portion and a female spacer portionthat is configured to receive the male spacer portion.
 8. The engine ofclaim 7, wherein one of the male spacer portion or the female spacerportion is integral to the engine housing and another of the male spacerportion or the female spacer portion is separable from the enginehousing.
 9. The engine of claim 1, wherein the spacer includes a malespacer portion and a female spacer portion that is configured to receivethe male spacer portion, the male spacer portion defining the supportsurface, the support surface including a flange that defines a portionof a water pump housing that houses an impeller of the water pump. 10.The engine of claim 1, wherein the engine housing includes a crankcasethat defines the exterior surface, the spacer extending from theexterior surface of the crankcase.
 11. The engine of claim 1, whereinthe engine housing includes a gear housing that houses one or moregears, the gear housing defining the exterior surface, the spacerextending from the exterior surface of the gear housing.
 12. The engineof claim 1, wherein the engine housing has a first side portion and asecond side portion that is opposite the first side portion, the enginehousing including a gear housing that houses one or more gears, the gearhousing being disposed on the first side portion of the engine horsing,the gear housing defining the exterior surface, the exterior surfacefacing the second side portion of the engine housing, the spacerextending from the exterior surface of the gear housing.
 13. The engineof claim 1, further comprising a timing chain, the balancer shaftdriving the timing chain.
 14. The engine of claim 1, further comprisinga timing chain, the water pump having an impeller, the balancer shaftdriving the timing chain and the impeller of the water pump.
 15. Theengine of claim 1, further comprising: one or more camshafts; a timingchain, the timing chain driving the one or more camshafts, the waterpump having an impeller, the balancer shaft driving the timing chain andthe impeller of the water pump; a first intake valve; and a secondintake valve, each of the first intake valve and the second intake valvebeing transitionable between a respective closed configuration and arespective open configuration, each of the first intake valve and thesecond intake valve having a respective lift amplitude corresponding tothe respective open configuration, the one or more camshafts definingthe respective lift amplitudes of the first intake valve and the secondintake valve, the respective lift amplitude of the first intake valvebeing greater than the respective lift amplitude of the second intakevalve.
 16. The engine of claim 1, further comprising: a cylinder boredefining a central axis; and a crankshaft defining a rotational axis,the rotational axis of the crankshaft extending along a plane that isparallel to the central axis of the cylinder bore, the central axis ofthe cylinder bore being offset from the plane.
 17. The engine of claim1, further comprising: a cylinder bore defining a central axis; abalancer shaft defining a rotational axis; a crankshaft defining arotational axis, the rotational axis of the crankshaft extending along afirst plane that is parallel to the central axis of the cylinder bore,the central axis of the cylinder bore being offset from the first plane;and a crankcase having a split that extends along a second plane, therotational axis of the balancer shaft and the rotational axis of thecrankshaft extending along the second plane.
 18. The engine of claim 1,further comprising: a cylinder bore defining a central axis, thebalancer shaft defining a rotational axis, the water pump having animpeller, the balancer shaft driving the impeller of the water pump; acrankshaft, defining a rotational axis, the rotational axis of thecrankshaft, extending along a first plane that is parallel to thecentral axis of the cylinder bore, the central axis of the cylinder borebeing offset from the first plane; and a crankcase having a split thatextends along a second plane, the rotational axis of the balancer shaftand the rotational axis of the crankshaft extending along the secondplane.
 19. The engine of claim 1, further comprising a monolithiccrankshaft, the engine being a single-cylinder engine.
 20. The engine ofclaim 1, further comprising a crankshaft defining a rotational axis andan oil bore that extends along the rotational axis of the crankshaft.21. The engine of claim 1, further comprising a crankshaft defining arotational axis and an oil bore that extends along the rotational axisof the crankshaft, the crankshaft having a bearing, the oil bore havingan outlet that is spaced apart from the bearing, the oil bore providingpressurized oil from the bearing to the outlet.
 22. The engine of claim1, further comprising: a crankshaft having a bearing; a rotor driven bythe crankshaft; a nozzle configured to spray pressurized oil onto therotor; and an oil flow path that provides pressurized oil to the bearingof the crankshaft and that provides pressurized oil from the bearing ofthe crankshaft to the nozzle.
 23. The engine of claim 1, furthercomprising an oil pan assembly that includes an upper oil pan portionand a lower oil pan portion, the upper oil pan portion having an opentop portion and an open bottom portion, the open top portion having aclosed bottom, the open bottom portion having a closed top, the loweroil pan portion being coupled to and separable from the open bottomportion of the upper oil pan portion.
 24. The engine of claim 23,wherein the closed bottom of the open top portion of the upper oil panportion has a drive shaft recess that is configured to at leastpartially receive a drive shaft of the vehicle.
 25. The engine of claim24, wherein the lower oil pan portion is laterally offset from the driveshaft recess and extends below the drive shaft recess.
 26. The engine ofclaim 23, wherein the closed top of the open bottom portion of the upperoil pan portion defines a dipstick access port.
 27. The engine of claim23, wherein the open top portion of the upper oil pan portion defines afirst plugged oil drain, and the lower oil pan portion defines a secondplugged oil drain.
 28. The engine of claim 23, wherein the lower oil panportion has a bottom that extends along a plane, the closed bottom ofthe open top portion of the upper oil pan portion has a slope relativeto the plane that facilitates providing oil from the open top portion ofthe upper oil pan portion to the lower oil pan portion.
 29. The engineof claim 23, the closed bottom of the open top portion of the upper oilpan portion has a drive shaft recess that is configured to at leastpartially receive a drive shaft of the vehicle, the lower oil panportion having a bottom that extends along a plane, the closed bottom ofthe open top portion of the upper oil pan portion having a sloperelative to the plane that facilitates providing oil from the open topportion of the upper oil pan portion over the drive shaft recess to thelower oil pan portion.
 30. An engine comprising: a water pump having aplain bearing that is supplied with pressurized oil; a balancer shaftthat drives the water pump; a water pump drive shaft, the water pumphaving an impeller, the water pump drive shaft driving the impeller; anengine housing; and a balancer driven gear housed in the engine housing,the balancer shaft driving the balancer driven gear, the balancer drivengear driving the water pump drive shaft, the balancer shaft being housedin the engine housing, the balancer shaft driving the balancer drivengear, wherein the balancer driven gear is disposed in a first side ofthe engine housing, the water pump being coupled to a support surfacethat faces a second side of the engine housing that is opposite thefirst side of the engine housing.
 31. The engine of claim 30, furthercomprising a spacer that defines the support surface, the engine housinghaving an exterior surface, the support surface of the spacer beingspaced apart from the exterior surface of the engine housing, the waterpump being coupled to the support surface and spaced apart from theexterior surface of the engine housing.
 32. The engine of claim 30,wherein the water pump drive shaft defines a first axis of rotation, thebalancer shaft defining a second axis of rotation, the first axis ofrotation being offset from the second axis of rotation, the water pumpdrive shaft aligning with the balancer shaft when viewed in a dimensionthat is perpendicular to the first axis of rotation.
 33. An enginecomprising: a water pump having a plain bearing that is supplied withpressurized oil; a balancer shaft that drives the water pump; an enginehousing having an exterior surface; a spacer that defines a supportsurface that is spaced apart from the exterior surface of the enginehousing, the water pump being coupled to the support surface and spacedapart from the exterior surface of the engine housing; a water pumpdrive shaft that extends through the spacer, the water pump having animpeller, the spacer having a tubular structure that defines a plainhearing, the water pump drive shaft having a proximal end portion and anopposite distal end portion coupled to the impeller, the water pumpdrive shaft extending through the plain bearing and driving theimpeller; and a radial seal ring disposed opposite the plain bearingfrom the proximal end portion of the water pump drive shaft.
 34. Theengine of claim 33, further comprising a compression spring that pressesthe radial seal ring.
 35. The engine of claim 34, wherein thecompression spring is disposed between the plain bearing and theimpeller along the length of the water pump drive shaft.
 36. The engineof claim 33, further comprising a water pump seal disposed between theimpeller and the radial seal ring.
 37. The engine of claim 33, whereinthe water pump drive shaft defines a first axis of rotation, thebalancer shaft defining a second axis of rotation, the first axis ofrotation being offset from the second axis of rotation, the water pumpdrive shaft aligning with the balancer shaft when viewed in a dimensionthat is perpendicular to the first axis of rotation.
 38. An enginecomprising: a water pump having a plain bearing that is supplied withpressurized oil; a balancer shaft that drives the water pump; an enginehousing having an exterior surface; and a spacer that defines a supportsurface that is spaced apart from the exterior surface of the enginehousing, the water pump being coupled to the support surface and spacedapart from the exterior surface of the engine housing, wherein thespacer includes a male spacer portion and a female spacer portion thatis configured to receive the male spacer portion, wherein the water pumphas an impeller and a water pump drive shaft driving the impeller, thewater pump drive shaft extending through the male spacer portion and thefemale spacer portion.
 39. The engine of claim 38, wherein one of themale spacer portion or the female spacer portion is integral to theengine housing and another of the male spacer portion or the femalespacer portion is separable from the engine housing.
 40. The engine ofclaim 38; wherein the male spacer portion defines the support surface,the support surface including a flange that defines a portion of a waterpump housing that houses an impeller of the water pump.
 41. The engineof claim 38, further comprising a balancer driven gear housed in theengine housing, the balancer shaft driving the balancer driven gear, thebalancer driven gear (hiving the water pump (hive shaft, the balancershaft being housed in the engine housing, the balancer shaft driving thebalancer driven gear, the balancer driven gear being disposed in a firstside of the engine housing, the support surface facing a second side ofthe engine housing that is opposite the first side of the enginehousing.
 42. The engine of claim 38, wherein the water pump drive shaftdefines a first axis of rotation, the balancer shaft defining a secondaxis of rotation, the first axis of rotation being offset from thesecond axis of rotation, the water pump drive shaft aligning with thebalancer shaft when viewed in a dimension that is perpendicular to thefirst axis of rotation.
 43. The engine of claim 30, wherein the waterpump drive shaft extends through the support surface.